package/qt5base: add optional dependency on udev

package/qt5base: add optional dependency on udev

Qt5 can optionally enable udev support, especially to enumerate input
devices dynamically. Without udev, devices are not properly enumerated,
and any device that is not present at launch time is never seen (there
is no support for hotplug, that is).

Currently, Qt5base has no explicit dependency on udev, so it will all
depend on the build order. Sometimes, a package that requires udev will
be built before qt5base and Qt5 will have support for udev, sometime no
such package is built before qt5base and Qt5 will not have support for
udev.

Add an explicit dependency on udev, but only if it is enabled.

Note: this only really requires libudev, but we do not yet have a
separate libudev; we still only have a udev provider (be it eudev or
systemd).

Signed-off-by: "Yann E. MORIN" <yann.morin@orange.com>
Cc: Cedric Chedaleux <cedric.chedaleux@orange.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
[Thomas: drop comment, as suggested by Arnout.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>